The present invention relates to plotters for recording graphic data such as figures in color on a sheet and, more particularly, to one which is capable of recording character data such as alphanumeric characters in combination with graphic data.
A prior art plotter includes a carriage driven in a first direction by a stepping motor amd a platen driven in a second direction perpendicular to the first by another stepping motor. A plurality of ball point pens are carried on the carriage to be movable toward and away from the platen. Each ball point pen is constantly urged toward the platen by a spring but, when out of operation, stopped by a solenoid operated mechanism. To plot graphic data on a sheet which is wound around the platen, at least one of the solenoid operated mechanisms is actuated to bring its associated pen into contact with the sheet and, then, the carriage and/or the platen is driven in the predetermined direction.
A plotter of the type described, however, is inherently slow in writing characters although successful to achieve a desired speed in drawing diagrams. This results from the fact that the carriage and platen are driven with a pen protruded into contact with the sheet, that is, the tip of the pen and the sheet are moved two-dimensionally relative to each other as in handwriting.
Meanwhile, a character printer known in the art has a multidot print head capable of printing out a vertical or horizontal string of pixels at a time out of a dot matrix which constitutes a character. Characters on one line may be printed out successively by one horizontal stroke of a carriage. Although this construction may offer fast printout operations for character data, the operating speed is quite low when it comes to graphic data because the horizontal stroke of the carriage has to be repeated a number of times while moving a platen to feed a sheet. Also, the resulting diagram will lack sufficient continuity in appearance.